An international research team led by Weill Cornell Medical College investigators has discovered an answer to why the human immune system ignores roughly 100 trillion beneficial bacteria that populate the gastrointestinal ...

Major recalls from two well-known ice cream companies due to the discovery of listeria bacteria raise questions about how the pathogen could have contaminated multiple ice cream manufacturing plants—and whether the discoveries ...

Crohn's disease is one of a family of chronic inflammatory bowel diseases (IBD). While it has already been proven to have genetic causes, scientists have now shown that the presence of certain intestinal bacteria also plays ...

Tick-borne diseases are a major public health problem around the world. Ticks carry and transmit a variety of microbes that cause disease. These illnesses, which include Lyme disease, Rocky Mountain spotted fever, and Tularemia, ...

An immune cell protein, ID2, is critical for the maintenance of healthy gut microbiota and helps these good bacteria fight off harmful bacteria, report scientists from the University of Chicago. The study, published in Immunity ...

Texas-based Blue Bell Creameries issued a voluntary recall Monday night for all of its products on the market after two samples of chocolate chip cookie dough ice cream tested positive for listeria, a potentially deadly bacteria.

If you're returning from abroad with a fever, your doctor will likely test you for malaria. You'll give multiple blood samples at the lab, and if the results are inconclusive, you'll face yet another round of tests.

In a remote part of the Venezuelan Amazon, scientists have discovered that members of a village isolated from the modern world have the most diverse colonies of bacteria ever reported living in and on the human body.

The bacteria [bækˈtɪərɪə] (help·info) (singular: bacterium)[α] are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals. Bacteria are ubiquitous in every habitat on Earth, growing in soil, acidic hot springs, radioactive waste, water, and deep in the Earth's crust, as well as in organic matter and the live bodies of plants and animals. There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water; in all, there are approximately five nonillion (5×1030) bacteria on Earth, forming much of the world's biomass. Bacteria are vital in recycling nutrients, with many steps in nutrient cycles depending on these organisms, such as the fixation of nitrogen from the atmosphere and putrefaction. However, most bacteria have not been characterized, and only about half of the phyla of bacteria have species that can be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology.

There are approximately ten times as many bacterial cells in the human flora of bacteria as there are human cells in the body, with large numbers of bacteria on the skin and as gut flora. The vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, and a few are beneficial. However, a few species of bacteria are pathogenic and cause infectious diseases, including cholera, syphilis, anthrax, leprosy and bubonic plague. The most common fatal bacterial diseases are respiratory infections, with tuberculosis alone killing about 2 million people a year, mostly in sub-Saharan Africa. In developed countries, antibiotics are used to treat bacterial infections and in agriculture, so antibiotic resistance is becoming common. In industry, bacteria are important in sewage treatment, the production of cheese and yoghurt through fermentation, as well as in biotechnology, and the manufacture of antibiotics and other chemicals.

Once regarded as plants constituting the class Schizomycetes, bacteria are now classified as prokaryotes. Unlike cells of animals and other eukaryotes, bacterial cells do not contain a nucleus and rarely harbour membrane-bound organelles. Although the term bacteria traditionally included all prokaryotes, the scientific classification changed after the discovery in the 1990s that prokaryotes consist of two very different groups of organisms that evolved independently from an ancient common ancestor. These evolutionary domains are called Bacteria and Archaea.